The invention relates to a tape guide system for a record carrier in the form of a tape, over whose guide surfaces the record carrier is passed; and more specifically, to a tape guide arranged in a cassette for the record carrier. Such tape guides are known in a wide variety of versions. The guide surface of such a tape guide may be circular-cylindrical or conical; however, it may also be constituted by a differently curved surface. Furthermore, such tape guides may be constituted by stationary parts or by rotatable rollers.
Examples of known tape guides are described in German "Auslegeschrift" 23 25 069 to which British Pat. No. 1,438,148 corresponds, and Austrian patent specification No. 290,159 to which U.S. Pat. No. 3,681,539 corresponds. Such tape guides may be arranged in a cassette which accommodates the record carrier, or outside the cassette on a recording and/or reproducing apparatus in the path of the record carrier, as is for example described in the Austrian Pat. No. 290,159. As is known, such tape guides should comply with special requirement i.e. they should guarantee a particularly uniform movement of the record carrier over the guide surface, without the occurrence of abrupt irregularities such as those which occur when the record carrier briefly sticks to the guide surface. It is equally important that the path of the record carrier over the tape guide is not disturbed with respect to its direction, in order to ensure that the record carrier, as it leaves the tape guide, is correctly fed to the next component with which it is to cooperate guide; such a component may for example be a magnetic head, a winding hub or a tape reel, or another tape guide.
When a tape guide is arranged inside the cassette it is of special importance that these requirements are met. This is particularly true with respect to uniformity of supply and take-up of the record carrier to or from the winding hubs in the cassette, to prevent contact between the record carrier edges and the bounding walls of the cassette. Such contact often occurs if the tape rolls are irregular. In all of these cases it is the uniformity of friction between the record carrier and the guide surface of the tape guide which is of importance for satisfactory guidance of the tape.
In this respect it may be noted that tapeguides arranged outside a cassette are also known in which the friction resulting from cooperation with the record carrier is improved by a special design of the guide surfaces. This concerns tape guide drums of comparatively large diameter for use in magnetic video tape equipment. For example in accordance with German "Auslegeschrift" 19 35 534, a corrugation is formed in the guide surface of the tape guide drum; and in accordance with German "Auslegeschrift" 19 08 508 inclined grooves are formed in the guide surface. The recesses thus formed in both cases are continuous channels which extend into the area of the guide surface over which no record carrier is passed. As a result the guide-surface area which produces the friction with the record carrier is reduced; but the friction is reduced mainly because air is admitted into the laterally open channels, so that air cushions are formed underneath the record carrier. These air cushions help support the record carrier.